Add polygon mesh support

[rjoomen]

No description provided.

[Levi-Armstrong]

Why do you have to use PolygonMesh directly versus using Mesh or ConvexHull type?

[rjoomen]

I was experimenting with meshing of point clouds (using PCL) and noticed PolygonMesh support was incomplete in an unexpected way. I agree it's not the best format, and also it's not supported in the contact checkers, but at least this makes some of the support for it more complete.

[rjoomen]

Is this good to go?

[Levi-Armstrong]

I think it is fine that the message interface supports the Polygon Mesh, but it should be converted it to a Mesh which is internally supported. I have code somewhere which will do this.

[rjoomen]

Is automatic conversion necessary? This PR simply enables communication of polygon meshes, what the user does with the data is up to him (including conversion).
Adding conversion functions to tesseract in general is useful though, but that would be a separate PR.

[Levi-Armstrong]

You have updated the to/from msg function and the Polygon class was never meant to be used directly but to avoid duplication between Mesh and ConvexMesh. Since to/from msg functions have been updated to handle this, it is unclear if this will be caught down stream like in the collision checkers which if they are not then this could cause issues which are not obvious. If this change is to be made I would want to updated the collision checkers to correctly handle this type or throw an exception.

[Levi-Armstrong]

I checked Bullet and FCL which will throw an exception if this geometry type is used, so I am okay with this change.

[rjoomen]

Thanks for checking!